In a walkway designed according to the traditional concept, all the elements forming it are fixed to a frame built with welded profiles forming a lattice with the necessary dimensions for supporting the loads of its own weight, the guiding elements, the drive, the enclosures of the walkway and the load of the users on the conveyor pallets.
The main problem with this concept is the inaccuracy it creates, requiring many hours for adjusting each of the parts linked to the frame such that they provide correct guidance for the pallets as well as easy assembly of the upper frame. Besides the complexity of the assembly, very precise and very complex tools are needed both for installing the assembly accurately enough and for manufacturing the actual frame.
Since the frame according to the traditional concept is manufactured in lattice form from structural profiles, a frame needs a large number of different parts for manufacture, making the assembly difficult and increasing the costs of the materials.
Finally, a walkway with a frame of welded structural profiles is very heavy, the total loads therefore not being completely optimized. Not only is the frame designed to support the weight of the parts forming the mechanism of the walkway but to also support its own weight.
Patent application EP1074507A1 proposes a walkway aimed at solving part of the problems of the traditional concept by means of frames of side panels forming a lattice and arranged laterally to the track of the pallets or steps of stairs. These side panels are joined to one another by means of welded crossbeams forming a closed frame. In addition to being expensive and rather non-productive, it is not compatible with the manufacture of modular frames or with field assembly due to the fact that it uses welded frames.
Other types of walkways have been proposed to solve these problems as disclosed in patent WO05070810A2. This patent describes a metal profile on which the tracks for the pallets transporting the users are directly manufactured. One of the features of this concept is the absence of a cover; the outer walls of the profile directly form the enclosures of the walkway and will therefore be exposed to all the external agents that the cover of a walkway is normally exposed to. Any damage to the outer walls of the profile requires the replacement of the entire profile, generating expensive and extremely complicated maintenance.
Furthermore, the use of the walls of the profile as the enclosure does not allow customizing the enclosure according to the demand, such enclosure being conditioned to the appearance of the actual guiding profile and to its dimensions, preventing different configurations thereof.
Using the guiding profile as a cover for the actual walkway means that when the walkway is underground it is impossible to access each of the supports to regulate it, making said walkway configuration impossible and allowing only one possible walkway configuration above ground level.
Patent document WO05070810 proposes the use of the same guiding profile and frame for supporting the glass of the handrail. This involves the use of excessive material considering that the supports for the glass are usually discrete and it would entail continuous support.
Patent document WO05070810 proposes a moving walkway with a frame manufactured from an extruded metal profile which can be used for guiding the pallets of the moving walkway, the support rollers of the pallets rolling on said extruded profile.
Extrusion is a process that makes it difficult to use steel because it obliges using considerably smooth shapes and considerable thicknesses, making it virtually impossible to manufacture a profile complying with all the requirements demanded of the guide concept of patent document WO05070810 in steel. Aluminum on the other hand presents problems as to its behavior regarding wear when it is used as a guide against the support rollers of the pallet.
The aluminum frame has much lower resistance than a steel frame and therefore, in comparative terms, a frame manufactured in aluminum must have more frequent supports than a frame manufactured in steel. This involves a larger number of parts and a more complicated assembly.
An extruded profile requires slides for assembling the screws that will secure the screwed connections and therefore wastes a large amount of material in the walls thereof that are not required in most of the length of the profile since the connections are only in certain points.
Making an aluminum profile entails increased costs because this metal has a high cost in comparison with its strength.